While Hillary Clinton was attacking presumptive Republican nominee Donald Trump in a foreign policy-themed speech, rival Bernie Sanders chose to talk about climate change, contaminated water in California and the country’s crumbling infrastructure.

Sanders spoke at a press conference in Modesto, California on Thursday, just days before the Golden State’s make-or-break primary.

“I have been all over this state, and I must tell you that I learned something that I did not know. I did not know that there were many, many thousands of homes in California where, when you turn on the faucet, the water that comes out is undrinkable.” he said. “This is a growing crisis. And that is why we have got to be loud and clear and join a number of counties in California that have already done the right thing” by banning fracking.

Much of his remarks focused on the threat of climate change.

“This is not just an environmental crisis, it is a national security one,” the senator from Vermont said, explaining that rising temperatures and decreased access to safe drinking water will lead to a massive humanitarian crisis, war and famine.

“What I am talking about is an unprecedented, aggressive transformation of our energy system,” Sanders said, adding that he would focus on tackling energy efficiency, while still trying to protect communities that are currently beholden to the fossil fuel industry. “Our goal is to save the planet, not to harm workers.”

Sanders attacked Trump for being a climate change denier, but refused to do the same for Clinton, the Democratic frontrunner. He called on Trump and his fellow Republicans to “understand that this crisis is real… this is a threat.”

“We need to stand up to the fossil fuel industry,” he said. “We need to let them know that their short-term profits are not more important than our children's future.”

Sanders called on Clinton to support a tax on carbon and a ban on fracking, not just regulations of the industry that she had pushed for as secretary of state.

“You did not hear me compare Secretary Clinton to Donald Trump. Donald Trump is a climate change denier,” he said. “What I did suggest is that I urge Secretary Clinton to be bolder. Of course she recognizes climate change is a problem.”

With Clinton and Sanders in a statistical tie in polling in California before the June 7 primary, the Vermont senator also focused on issues affecting residents of the state, including the massive, multi-year drought and that thousands of people in the Golden State cannot drink unfiltered water from their taps.

Clinton currently leads Sanders 49 percent to 47 percent among likely Democratic voters, according to an NBC News/Wall Street Journal/Marist College poll. The two-point spread is within the survey’s margin of error.

During the question-and-answer period, once Sanders finished addressing climate change queries, he moved on to the “gossip.”

Much of the remaining eight minutes of the 35-minute press conference focused on superdelegates.

“This whole superdelegate process, frankly, is absurd,” Sanders said. “Hillary Clinton won the support of over 400 superdelegates before anybody else was in the race, eight months before the first ballot was cast in Iowa. Does that make sense to anybody?”

“To the degree that you want to give any credibility to the concept of superdelegates, what a superdelegate is supposed to do is look around and say, ‘Okay, my job is to make sure that Democrats do well. Which candidate can do well and can beat Republicans?’”